A polylactide (or polylactic acid) resin is a kind of a resin including repeating units represented by General Formula below. Unlike existing crude oil-based resins, the polylactide resin is based on biomass, which is usable as a renewable resource, and less discharges CO2 which is a global warming gas, in production, as compared to the existing resins, and has appropriate mechanical strength corresponding to the existing crude oil-based resin, together with eco-friendly characteristics such as biodegradability by moisture and microorganisms when being buried.

As a preparing method of the polylactide resin, a method of directly polycondensing a lactic acid or a method of ring opening polymerizing a lactide monomer in the presence of an organic metal catalyst has been known. In the direct polycondensation among the methods, a viscosity is rapidly increased while processing the direct polycondensation, such that it is significantly difficult to effectively remove moisture which is a reaction by-product. Therefore, it is difficult to obtain a polymer having a high weight average molecular weight of one hundred thousand or more, such that it is difficult to sufficiently secure physical, mechanical physical properties of the polylactide resin. Meanwhile, since a lactide monomer is firstly prepared from a lactic acid in the ring opening polymerization method of the lactide monomer, a complicated preparation process and high cost are required as compared to polycondensation. However, a resin having a relatively large molecular weight may be relatively easily obtained by ring opening polymerization of lactide using the organic metal catalyst, and a polymerization rate may be easily controlled, which is commercially available.
The polylactide resin has been mainly used as disposable packaging/containers, coatings, foamings, films/sheets, fibers, and the like. Recently, an effort to mix the polylactide resin with existing resins such as acrylonitrile butadiene styrene (ABS), polycarbonate, polypropylene, and the like, to reinforce physical properties, thereby providing semi-permanent usages such as a cell phone exterior material, an automobile interior material, and the like, has been actively conducted. However, the polylactide resin has physical weaknesses such as hydrolysis due to factors such as a catalyst used at the time of preparing the polylactide resin, moisture in the air, and the like.
In particular, when the polylactide resin, the copolymer including the same, and the like, are processed as a film form and used as a disposable packaging material, the physical weaknesses such as fragility against impact and deteriorated flexibility may be obstacles to expansion to various markets.